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battery life

06-09-2007, 04:03 PM

As a occasional user of my cordless drill on weekends, I often find the battery very low when I need it (which admittedly is not every weekend). Is there any truth that keeping the battery in the refigerator will extend its useful life? Are there any techniques to increase its ability to hold its charge longer? About how long should a fulled charged battery hold its charge if it isn't used at all?
Thanks for any input.

First of all, welcome to the group. You didn't say whether or not your drill is a Ridgid or not but I'll assume it is. According to the owners manual that came with my Ridgid drill/driver it says; "If you store your tool for long periods of time without using it, recharge the batteries every month or two. This practice will prolong battery life."

The refrigerator/freezer theory has been around for awhile but personally I think it's nothing but urban legend stuff. I tried it with a DeWalt battery once and noticed no difference at all in the run time.

I decided to change calling the bathroom the "John" and renamed it the "Jim". I feel so much better saying I went to the Jim this morning.

Comment

Keeping an Alkaline battery cold will prolong it's life, but it doesn't impact rechargable batteries at all as far as I know. Although using a battery that is cold does give a shorter runtime, because the chemistry needs warmer temperatures to work propery. The Lithium-Ion type betteries keep warm using the battery charge itself to work at full potential.

Matt

Comment

Heat is what kills a battery. At room temp they should be fine. What you don't want is to have them in say a closed up car on a hot sunny day or near your furnace. As for alkaline cells like Duracell and Energizer, they store fine at room temp, longer if say around 40F, but in a hot car over the summer you'll really shorten their life. Putting a power tool battery in the fridge won't harm it, but it's really not needed. If it won't hold a charge for 2 months at room temp that battery is bad. Unused batteries should be put into a tool and run until it just gets sluggish. Then STOP... Do not run a battery all the way down. After discharge, charge it back up and put it away. I've found with Li-ion batteries that have been sitting for a few days that a quick 5 minute boost is good just before you put them into use. Again, it's best not to let them run all the way down. Once you tell they are running down, stop and after a few minutes to cool, put it in the charger and charge it up.

Comment

There is a lot of misinformation and disinformation floating around about NiCad batteries. Even the good sources, seem to disagree, but when you delve further you will find that many of the differences are related to the different uses. For example, some people, like Remote Control car racers, will discharge cells individually...not as a pack. This allows them to do things differently than a typical tool user.

Your occasional use, as a weekend warrior...or worse...someone that might use a tool once every few months, is one of the hardest on NiCads. Ideally, they need to be cycled, to maximize their potential and keep them "fresh." However, even with your use, there are things you can do to improve their life.

1. NiCads selfdischarge....as much as 20&#37; the first day (depending on heat.) The selfdischarge rate is proportional to temperature...it can double or triple at high heats...such as in a car. Keeping a NiCad cool WILL reduce the selfdischarge rate...but not stop it. They WILL selfdischarge considerably slower in the refrigerator than they will in your 75 degree house...and much slower than they will in your 120 degree car.

2. Heat damages NiCads and shortens their life. Heat can happen during charging, use or storage. Keep them cool as much as possible!!! Let the batteries cool down after use, before recharging. Don't leave your tools sit in the sun.

3. Exercising a pack, by running it down to about .3 volts per cell, will help the pack life. Going below that voltage risks reversing a cell and damaging that pack. Run them down till you see a drop in tool performance...but don't keep running them down after that. Do not leave them go flat in a flashlight.

4. NiCads are less efficient at low temperatures. Let them warm up before using them...especially if you keep them in a cool place to reduce their selfdischarge.

5. It is OK to top off a pack right before you use it, but don't top it off and put it back on the shelf.

6. In general, trickle charging is bad for packs. It is more convenient for you, because the pack will always have it's maximum capacity...but the maximum capacity will go down because of the constant heat from the trickle charging...eventually having very little reserve or failing altogether.

Comment

There are a few tricks to keeping batteries charged for intermittent use but realistically the most practical is to just leave it in the charger. This is not a problem with most chargers with a self maintenance feature. Verify that before as you don't want to end up overcharging which is worse ( and possibly dangerous). If you mostly use it on weekends try making it a habit of popping them in the charger every friday. Even if you don't end up using the tool its healthy to keep recharging the batteries occasionaly and not let them drain too far. That also insures they will have enough charge to do smaller jobs in between charges.

The easiest solution for the occasional user is also the most expensive. Get lithium ion battery tools. They hold close to a full charge for about 18months.

Keeping the batteries stored in cool or cold places is no myth. There are extensive studies and documentation on this ranging from NASA to all battery manufacturers. Batteries perform best within a specific temperature range. Not too cold and not too hot. Heat will rapidly deteriorate not only a batteries self discharge rate but also its lifespan. In other words don't store the batteries in your car in the middle of a summer day. Cool batteries will last longer and hold their charge better.

NiCad batteries will hold a charge almost indefinately at very cold temperatures. Anywhere from 1 to 5&#37; loss per month as opposed to per day. It is not recommended for end users to keep them in the fridge because of condensation. You would need to store them sealed and wait for them to warm up to ambient temperature before unsealing them and using them unless you want to risk a shorted and damaged battery pack.

When it comes to Lithium Ion cool storing is essential to maintaining their life. Lithium Ion ion cells naturally loose about 10-20% of their maximum charge capacity every year regardless of anything. Thats simply their primary flaw. Note that I'm referring to capacity, not charge. That means a Lithium battery will still have 95% of its charge after a year but it maximum capacity will have degraded by 10-20% permanently. All Lithium Ion manufacturers recommend storing for extended periods at 40% charge and at around 20-30F. Merely storing them at 40% charge will cut off the yearly capacity loss by about half. That goes against the conventional wisdom of storing batteries topped off for extended periods. In addition to that, the colder they are stored the better going down to about 20F. At 40% charge and 20F a Lithium battery will only loose 1 to 5% capacity loss per year. Its recommended you never buy more lithium batteries than you need because of this. As they wear out, when you buy new ones that insures you have a battery with recently manufactured cells. Basically when you go to Home Depot to buy a shiny new Makita or Ridgid lithium Ion tool set, avoid the dusty box in the back of the bin thats been sitting there for a year because the employees don't cycle them to the front The batteries will already likely be degraded.

It is not recommended for end users to keep them in the fridge because of condensation. You would need to store them sealed and wait for them to warm up to ambient temperature before unsealing them and using them unless you want to risk a shorted and damaged battery pack.

While this seems logical...that condensation might be an issue, I've never experienced a problem with it in any tools and I always store my tool batteries in the fridge. Also, I have experienced plenty of condensation built up on tools just from taking them from in my cool, air conditioned house outside on a hot muggy day. I've had tools literally sweating water from doing this.

As was mentioned before, if you store your batteries in the fridge you need to let them warm up before using them because at cold temperatures they are very inefficient and you will probably get even less power than you would if you left them lying around in the heat. One way to quick warm them is to pop them back into the charger for a few minutes.

There are a few tricks to keeping batteries charged for intermittent use but realistically the most practical is to just leave it in the charger. This is not a problem with most chargers with a self maintenance feature. Verify that before as you don't want to end up overcharging which is worse ( and possibly dangerous). If you mostly use it on weekends try making it a habit of popping them in the charger every friday. Even if you don't end up using the tool its healthy to keep recharging the batteries occasionaly and not let them drain too far. That also insures they will have enough charge to do smaller jobs in between charges.

I've had some bad experiences with leaving batteries on chargers and have totally lost confidence in using them as maintenance chargers. In my experience, most of them just apply a very low charge current. While this will keep them topped up, it will also damage the batteries in two ways.

1. It will convert the cell...little by little, into a non-recoverable mode....reducing the capacity.

2. The constant heat will prematurely age the batteries...causing a failure across the plates.

Ideally, a good maintenance system would periodically discharge the batteries to a certain level than SLOWLY recharge them to help balance the cells. In fact, this is how good RC chargers work. They have a "recovery" and new battery mode will they will take the battery through several charge-discharge cycles. This maximizes the capacity of the battery.

Comment

I've had some bad experiences with leaving batteries on chargers and have totally lost confidence in using them as maintenance chargers. In my experience, most of them just apply a very low charge current. While this will keep them topped up, it will also damage the batteries in two ways.

1. It will convert the cell...little by little, into a non-recoverable mode....reducing the capacity.

2. The constant heat will prematurely age the batteries...causing a failure across the plates.

Ideally, a good maintenance system would periodically discharge the batteries to a certain level than SLOWLY recharge them to help balance the cells. In fact, this is how good RC chargers work. They have a "recovery" and new battery mode will they will take the battery through several charge-discharge cycles. This maximizes the capacity of the battery.

I know, you're correct but I should have elaborated a bit more. What I mean is that most ocassional users don't care enough to bother cycling batteries into the charger ocassionally, only when needed which will more than likely mean batteries that stay close to or fully discharged for long periods. That is worse for the battery that the comparatively smaller damage extended trickle charging and heat will cause. In this case you're probably better off leaving them in maintenance mode on the charger. Some chargers are better than others at this.